The present invention relates to an electronic circuit, a driving method thereof, an electro-optical device and electronic apparatus, which drives an electrical current-driving type element such as an organic light-emitting diode element.
In recent years, an organic light-emitting diode (hereinafter, referred to as OLED), which is called as an organic electroluminescent element or a light-emitting polymer element, has been drawing attention as a next generation light-emitting device that replaces a liquid crystal display device. The OLED element has low viewing angle dependency because it is a self-luminous type, and it does not need a backlight or a reflected light. On this accounts, it has excellent characteristics as a display panel, such as wide viewing angle, low power consumption and adaptability to being made thin.
Herein, the OLED element is an electrical current type passive driving element in which a light-emitting state can not be maintained when the electrical current is cut off, because it does not have a voltage holding characteristic like a liquid crystal element. For this reason, when the OLED element is driven in an active matrix method, a configuration is generally used in which a voltage corresponding to gray scale of a pixel is applied to a gate of a driving transistor, the voltage is hold by the gate capacitance, and a current corresponding to the gate voltage is input to the OLED element by the driving transistor, during a writing period (selection period).
By the way, in such a configuration, as a threshold voltage characteristic of the driving transistor is deviated, the brightness of the OLED element is different for each pixel, and accordingly it has been pointed out that the display quality is deteriorated. In order to solve the problem, recently, techniques has been suggested that during the writing period, the corresponding driving transistor is connected to a diode and a constant current is input to a data line from the driving transistor, and thereby it is programmed that the gate of the driving transistor is applied with a voltage corresponding to the current to flow into the OLED element to compensate for the deviation of the threshold voltage characteristic of the driving transistor (for example, see Patent Documents 1 and 2).
[Patent Document 1] U.S. Pat. No. 6,229,506 (see FIG. 2)
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2003-177709 (see FIG. 3)
However, according to the techniques, in a case that the driving transistor is a p-channel type, during the writing period, when a current flowing into the OLED element is set in a small amount, the gate voltage of the driving transistor is high, so that a current between the source and drain of the driving transistor is in a state in which it is difficult to flow. For this reason, it has been newly pointed out that the required voltage cannot be applied to the gate of the driving transistor during the writing period.
The present invention is designed to solve the above-mentioned problems, and it is an object of the present invention to provide an electronic circuit, a driving method thereof, an electro-optical device, and electronic apparatus, which are capable of applying to the gate of the driving transistor a voltage corresponding to the current which is to flow into a passive driving element.